A light emitting device is an inorganic semiconductor device that emits light through recombination of electrons and holes. A UV light emitting device emits UV light and can be used in various fields including curing of polymer materials, sterilization of medical equipment, device components, light sources for generation of white light, and the like. As such, UV light emitting devices have been increasingly used in various fields.
Like typical light emitting devices, the UV light emitting device includes an active layer interposed between an n-type semiconductor layer and a p-type semiconductor layer. The UV light emitting device emits light having relatively short peak wavelengths (generally, peak wavelengths of 400 nm or less). Thus, in fabrication of the UV light emitting device using a nitride semiconductor, there can be a problem of absorption of UV light emitted from the active layer into n-type and p-type nitride semiconductor layers when the n-type and p-type nitride semiconductor layers have smaller band-gaps than energy of UV light. As a result, the UV light emitting device suffers from significant deterioration in luminous efficacy.
Thus, in order to prevent deterioration in luminous efficacy, the UV light emitting device contains a certain amount of Al in the active layer and a nitride semiconductor layer at a UV light emitting side. However, since GaN has a band-gap of about 3.4 eV and absorbs light having a wavelength of about 360 nm or less, Al must be contained in the nitride semiconductor layer in order to emit light having a shorter wavelength than this wavelength. As the band-gap increases due to the presence of Al, ionization energy of holes increases together with decrease in activation rate, such that hole injection efficiency into the active layer is reduced. In order to solve this problem, although there is a conventional technique wherein plural layers having different concentrations of p-type dopants are alternately stacked one above another to provide lateral hole dispersion based on a difference in doping concentration between the layers, this technique provide insignificant hole dispersion and cannot sufficiently suppress deterioration in hole dispersibility of the UV light emitting device.